Enhancement of growth of virulent strains of Escherichia coli by interleukin-1.

Interleukin-1 (IL-1) is a polypeptide cytokine that mediates many physiological responses to infection and inflammation and is a growth factor for certain mammalian cells. Virulent and avirulent clinical isolates of Escherichia coli were grown in culture media in the presence of human IL-1. IL-1 beta, but not tumor necrosis factor or IL-4, enhanced the growth of virulent, but not avirulent, E. coli. This enhancement was blocked by the IL-1 receptor antagonist (IL-1ra). Radiolabeled IL-1 bound to virulent but not avirulent E. coli in a specific and saturable fashion; IL-1ra inhibited this binding. Thus, human IL-1 may recognize a functional IL-1-like receptor structure on virulent E. coli and may be a virulence factor for bacterial pathogenicity.